Unloading mechanism



oct.- 4, 1927.' 1,644,007

H. T. BLOM UNLOADING MEGHANISM` Filed June 20, 1921.

IIIIIIIIIIIH pressure cylinder.`

Patented @et 4, 1927.

UNITED STATES' 1,644,001 PATENT oFF-ice.

nJaLMAn fr. BLOM, or. cercado, ILLINOIS, ns'sieivon 'no sULLvAN MACILINEEY come PANY, A conronA'rfIoN, on Mietssacnusnfrrs;

-UNLoAD-LNG lvrncnnivisivr.`

Application filed June, 20,

This; invention relates to unloading mechanism for compressors, more particularly to auxiliary .unloadingvalves employed in connection with the highstages of multistage` CompressorsV to prevent excessive temperatures in theA high stage or stages when the inlet to one of the lower stages` isclosed by the main unloading device.

The. invention has for itsobject to gene-r.- ally improve devices of this character, and more particularly to provide means controlled by subnormal cylinder pressure for positively opening communication between the end or ends of the cylinder and the atmosphere', thereby insuring the proper vventing of' the compressor independently of or prior to the development of pressure therein, to provide a single relief valve for the purpose in questionadapted to cooperate with both ends of double acting' cylinder; to providean auxiliary unloading or relief device which will cooperate with the compressor mechanism beyond the discharge valve or valves thereof to divert the discharge from the compressor from the receiver to the atmosphere, thereby avoiding the necessity o't pumping against receiver pressure while preventing escape of the latter during the time the compressor is unloaded.; and to provide means for insuring` the return of the parts of the auxiliary unloader to normal position when the main unloader is operated to load the compressor.

foregoing and other objects of the invention, together with means whereby the same may beV carried` into. effect, will best be understood from the following description of one form orf embodiment thereof in which:

1 is a side elevation of a two-stage compressor having the invention applied t iereto. y y

Fig. 2 is an enlarged detail vertical section of a portion of the high pressure cylinder, taken substantially on liney 2 2 of.l Fig. 1.

Fig. 3 is'v a still further enlarged horizontal section, taken substantially on the lines 3 3 of Figs. 1 and 2, of they auxiliaryunloader and adjacent portions of the high The invention is herein illustrated asapplied to a compresser of the angle-compound type havinga horizontal low pressure double acting cylinder l, a highv pressure double illustrated in the accompanying drawings,r

acting vertical cylinder 2, and driving mechanism for the pistons reciprocalolein these cylinders whereby the two stages are oper'.- ated from a single crank shaft 3. T heintake to the low pressure cylinder 1 yis through yan inlet pipe 4 provided withan automatically operated main unloading mechanism 5 suchy as is commonly used to unload the-compressor when the discharge pressure thereofr exceeds a predetermined amount. The air or other fluid under partial compression passes from the first stagercylinder 1 through an` intercooler 8 to the, high stagecylinder 2 and thence, after final' compression, through a discharge pipe 6V tothepoint of utiliza-tion or, as herein shown, tof afreceiver 7. Y y y llVhen the pressure in the receiver'or other system suppliedv by the compressor `rises above the predetermined normal operating pressure, the unloading mechanism isv operated in a well-knownzmanner to close the inlet 4 tothe low pressure'cylinder 1 to prevent the intake of air through the inlet and hence the operationof the compressor to force more air into the main or receiver.l

However, due to leakage or other causes, a certain amount of air will pass` this/cylinder into the intercooler and will be compressed in the high pressure cylinder 2from atmospheric pressure, or from below atmospheric pressure, to the maximum pressure in the receiver. This highcompressionfrom a low initial pressure results in an objectionably 'hightemperature in the highpressure cylinder, andl in order to prevent such anV occurrence there is usually vprovidedanauxiliary unloader or relief device which, ,when the main unloader- 5 is operated' to unloadV the compressor by closing the intake 4, thereby causing the pressure inthe system to fall below normal', will operate to ventltliehigh pressure cylinder H2 in such a manner as to prevent kthe compression of such airl or other( fluid as may findiits Way thereinto. The present invention relates to improve- Vmentsin devices of the latter character and,

in` accordance therewith, the following construction and arrangement are ypreferably employed. I

Referring tovFigs. 2 andl 3, the cylinder 2 is provided :with valve chambers lO'containing intake and exhaust valves 11 and 12 respectively, the former controlling communication between the interior'ot the cylinder and intake chambers 13 communicating with the conduit 1.4 leading from the intercooler 8, as is usual in compressors of the type shown. At the discharge side of the discharge valves 12, the valve chambers at the opposite ends of the cylinder are connected by a passage 15 formed in the cylinder 2 and separated by a partition 16 from the main discharge passage 17 which communicates with the pipe 6 leading to the receiver. The passages 15 and 17 communicate respectively with chambers 18 and 19 formed in Aa casing 20 secured to the side of the cylinder 2. The chamber 19 is closed at its outer end by a head 21 and encloses a valve cage 22 carrying a check valve 23 adapted, in the normal operation of the compressor, to permit flow from the passage 15 and chamber 18 through the chamber 19 to the discharge passage 17, said valve, however, preventing iiow in the opposite direction. The check valve 23 is preferably of liat annular form and is normally held seated by a suitable annular spring 24.

l The chamber 18 communicates, through a port 25 in an auxiliary casing 26 secured to the casing 20, with a passage 27 in the latter casing, said passage 27 communicating with a chamber or passage 28 formed in the casing 2O and having a port 29 opening to the atmosphere. rlhe port 25 is normally closed by a valve 30 which maybe unseated, as hereinafter explained, to open communication between the passage 15 and the atmosphere through the chamber 18, port 25, passage 27, chamber 28, and port- 29, thechcck valve 23 at this time preventing backward flow of fluid. from the discharge passage 17 and receiver 7 to the chamber 18.

For the purpose of operating the valve 30 to unseat the same, there is provided a piston 31 operating in a cylinder 32 formed in the auxiliary casing 26, said piston cooperating with the stem of a pilot valve 34 carried by the valve 30 and controlling a port therein. The pilot valve stein 33 is guided in the stem 36 of the valve 30 and is provided with a shoulder 35 adapted to engage the end of the valve stem 36 and unseat the valve 30 after the pilot valve 34 has been unseated to relieve the pressure on said valve 30, thereby facilitating the unseating of the latter. The pilot valve stem 33 extends through the inner head of the cylinder 32 (which is preferably formed with a suitable guide for said stem), is engaged at its outer end by the piston 31, and is provided with a collar 37 between which and said inner cylinder head is interposed a spring 38 tending normally to hold the valves 30 and 34 seated. The cylinder 32 is closed at its outer end by a head 39 having an atmospheric port 40 and is formed adjacent its inner end with a shoulder 41 against which the piston 31 is adapted to seat when said piston is moved inwardly, as hereinafter explained, in order to prevent leakage past said piston.

rllhe inner end of the cylinder 32 communicates, through passages 42, 43, and 44 formed respectively in the casings 26 and 20 and the wall of the cylinder 2, with a nipple 45 which bridges the cylinder water jacket 46 and communicates with the interior of the cylinder at substantially the longitudinal center of the latter. 'Seated at the mouth of the passage 42 is a bushing 47 providing a seat for a check valve 48 which is normally seated by a spring 49. rllhe check valve 48 is provided with a stem 50 which extends through the bushing 47 and has its end disposed in the path of movement ofthe piston 31, whereby said check valve will be held unseated except when said piston is in a position to permit the seating of the valves 30 and 34 by the spring 38.

In operation, when the main unloader 5 is operated to close the intake 4 and unload the compressor, the condition of partial vacuum or subnormal pressure, crea-ted Vin the cylinder 2 behind the piston 51 therein, is communicated through the nipple 45 and passages 44, 43, and 42 to the check valve 48, causing the latter to be unseated and admit said subnormal pressure to the inner end of the cylinder 32, Thereupon the atmospheric pressure admitted to the outer end of the cylinder 32 through the port 40 will cause the piston 31 to move. inwardly, unseating the pilot valve 34 and thereafter the valve 30, thereby opening the passage 1 5 to the atnwsphere. rEhe/receiver pressure acting through thc passage 17 will then hold the check valve 23 firmly seated, and any fluid passing through the high pressure cylinder 2 will be immediately discharged to the atmosphere without substantial compression.

lVhen the compressor is loaded, the condition of subnormal pressure Vin the cylinder 2 is replaced by one of normal pressure which will be communicated to the inner end of the cylinder 32, thereby causing the piston 31 to move outwardly and permitting the valves 30 and 34 to be seated to close the port 25. ln this connection it will be observed that, by reason of the engagement of the valve stem 50 with the piston 31, the check valve 48 will beheld open, admitting pressure to the inner end of the cylinder 32 until the piston 31 has been moved outwardly to a sulticientextent to permit the seating of the valve 30, thereby insuring the return of the parts to their normal position,'whereupon the valve will be seated by the increasing pressure in the chamber 18 assisted by the spring 49. Thereafter, the pressure in the passage 15 and chamber 18 will be built up until it equals or exceeds that in the passage 17 and receiver 7, whereuponvthe check valve 23 will open to permit communilll() lll) l for illustrative purposes merely,

cation. between thepassagesul and; 17 and the disch-arge of the. compressed luidA into thelreceiven in the usuali manner.

It Will. thus be seen that the invention pro; vides an extremely simple mechanism for preventing-the development of'excessive heat inthe high pigessure cylinder o-amultistage compressor` d ue. to high compression oi the fluid? from an initial subnormal: pressure, said mechanism4 being positive4 andv reliable its. operation and acting, under. the. influence of subnormal pressure in the compressory cylinder, to disconnect the latter from the usual2 receiverand permitA the same to dischargeto the atmosphere, the. pants being Vso constructed` rand arranged as. toA insure their return to normal'conditionv and' permit the normal operation ofthe-compressor when the main unloading` mechanism is operatedto load 7th-ecompressor, or when the conditions Within the compressor` are. otherwise. returned to normal.,r

llV'hile If' have in this application specifically described one embodiment Whichmy Vinvention may assume/in-.practice,litv is-to been chosen and that the invention nmay be otherwise embodied` and practiced' Without departingY from its spirit or the scope or' the appended claims.

hat I-'claim as-ne-vvand desire to secure by Letters Patent is: f

1. The combination with a compressor, of means,k for directly controlling compressor cylinder fluid to effect unloading-Lof said compressor, and means responsive to sub-normal pressure Within said compressor for operating said unloading means, said unloading means including a plurality ofi-valve elements adapted to besuccessively actuated and fluid pressure controlled actuating means for said valves.

2. The combination with a. compressor cylinder, of; means forv unloading said cylinder comprising a valve Whose opening eliminates compressive action, said valve opening againstarluid pressure produced in` saidcylinder, and means responsive to subnormal pressure "inv saidcylinder for opening said valve.

3. The'combination with a compressor c-ylinder, ofemeans for' unloading the same comprising a normally closed valve opening toivard's the cylinder and upon which compressor discharge pressure exerts. a force to maint-ain the same closed, and' means responsive tosubnormal pressure Within the cylinder for positively moving said valve to open position,Y i

i 4*. The combination with a double acting compressor, vof meansv arranged rbetween the opposite ends o the cylinder and comprising ay valve Whose opening Veliminates compressive act-ion at both endsof said cylinder for unloading the latter, and means responsive be understood that this form has to subnormala: pressure. .in said; cylinder i for opening. saidI valve. f I

5 A The combinat' on with .acompressor halving a, cylinder, said compressor of' a relief Vvalve vfor` venting to the atmosphere., and

means responsiveto subnormal. pressure vvithin saidcompressor cylindielnfor opening said reliefvalve.

6; The combination` with a. compressor cyl:-

inder, of. a. relief valve for ven-ting, both endsv ovfsaidl cylinder tothe atmosphere, and means responsive to subnormal'` pressure Within said -A compressor cylinder for 4openi-I-igsaid relief valve, 7'. rPhe combination with ay compressor havinga cylinder and means for normally-ref ceving.. the discharge from said compressor, ofv means responsive to. 'variations in presf sur-,einsaid compressor cylinder for. diverting.V said. means. v

8. The combination with acompressorhaving discharge valves and Withmeansfor normally receiving the discharge from saidicompressor, of; means includinga valve opening against the discharge, pressure responsive to variations in pressure in compressor. at a point short of saidl discharge valves pr diverting said-.discharge fromx said receiving means. l, f

9i Thecombination with` a compressor having discharge valves, of,4 means'orreceiv-ing the` discharge through* said valves, and means having. direct communication .with the compressor. cylindery and being. responsive discharge from said receiving ico to variations inpressure in. said compressor' for! opening. a. separate ldischargefat af; point beyond'- 'said discharge valves.

l0; The combination with a compressor having a low pressuretcylinder, unloading means-therefor, ahigh pressure cylinder, and discharge valvestherefor, means for receiving the discharge throughC said discharge valves- When-,the'compressoris loaded, and

means; having direct communication with the high pressure cylindery andgbei-ng.l responsive toi variations-in pressure therein; upon unloading of said low-pressurev cylinder for diverting any discharge at a point beyond said discharge valves fromV saidgreceivf.

with the central vpart ot the compressor cylinder.

'12. The combination with a compressor 'having a cylindenand'means fornormally receivmg the dischargeiffrom' saidf compressor, of'means for diverting said discharge from said receiving means to the atmosphere, and meansv responsive to subnormal pressure in said compressor cylinderfor operating said diverting means.

13. The combination with a compressor and means for nbrmally receiving the discharge from said compressor, of means for diverting said discharge from said receiving means to the atmosphere', and means responsive to subnormal pressure in said compressor for operating said diverting means against the discharge pressure during existence of the subnormal pressure.

14. The combination with a compressor having cylinders, of a relief valve'for venting said kcompressor to the atmosphere, a cylinder directly communicating with the interior of a compressor cylinder, and a piston in said cylinder for operating said valve to cause it to be positively actuated to effect its venting function.l

15. The combination with a compressor cylinder, of a relief valve for venting said compressor cylinder to the atmosphere, a cylinder` communicable with the interior of the compressor cylinder, a one-way check opening towards the compressor cylinder controlling the communication between the latter and the second mentioned cylinder, and a piston in said second vmentioned cylinder for opening said relief valve.

16. The combination with a compressor having` a cylinder and a discharge passage, of a chamber con'nnunicating with said discharge passage and having a port communieating with the atmosphere, a cylinder having its ends commruiicating respectively with the atmosphere and with the interior of said compressor cylinder, a valve for controlling said port, and a piston in said cylinder and cooperating with said valve to unseat the same.

17. The combination with a compressor, of a relief valve for venting said compressor to the atmosphere, a pilot valve carried by said relief valve, and means responsive to variations in pressure in said compressor for unseating said pilot valve and for .thereafter. unseating said relief valve.

18. The combination with a compressor, of a relief valve for venting said compressor to the atmosphere, a pilot valve forsaid relief valve, a cylinder communicating with the interior of said compressor, andv a piston in said cylinder for successively operating said pilot and relief valves.

19. The combination with a compressor, of a relief valve for venting said compressor -to the atmosphere, sai-d relief valve having astem, a pilot valve carried by said relief valve, said pilot valve having a stem passing through the stem ofvsaid relief valve and provided-with a shoulder adapted to engage said relief valve stem, and means responsive to variations in pressure within said compressor and cooperating with saidv pilot valve stem for successively unseating said pilot and relief valves. 1

20. The combination with a compressor having a discharge valveand means'for normally receiving the discharge from said compressor, of unloading means responsive to variations in pressure in said Vcompressor and including a relief device interposed between said discharge valve andreceiving means.

21. The combination withA a compressor having a discharge valve and means for normally receiving` the discharge from said compressor, of unloading means responsive to variations in pressure in said compressor and including a relief device interposed between said discharge valve and receiving means, and a check valve interposed between said relief device and receiving means.

29.. The combination with a compressor cylinder' having a discharge-valve, a passage communicating with said discharge valve,

and a separate discharge passage, of a Cas-,l

ing having chambers communicating with said passages respectively, a check valve interposed between said chambers, the chamber communicating with the passage from the discharge valve having a port, and a relief valve responsive to variations `in pressure in said cylinder for controlling said port.

' 23. The combination with a compressor having a discharge valve and means for normally receiving the discharge from said con'ipressor, of a relief device interposed between said discharge valveand receiving means, and means responsive to subnormal pressure within said compressor for operatf ing said relief device.

24. The combination with a cylinder of a double acting compressor, of an auxiliary unloader for said compressor comprising a single relief device cooperating to vent simultaneously both ends of said cylinder and responsive to variations in pressure within said cylinder.

25. The combination with a double acting compressor comprising a cylinder, discharge valves at the opposite ends of said cylinder operative to permit discharge of `air during normal loaded ruiming, and a passagev connecting said valves, of a relief device communicating with said passage and responsive to variations in pressure within said cylinder.

26. The combination with a cylinder of a double acting compressor, of a single relief device cooperating to relieve both ends of said cylinder, and means communicating with said cylinder at a` point intermediate the clearance volumes of the cylinder and responsive to variations in pressure therein Vfor operating said relief device.

llO

' with 'said passage for receiving the discharge from said compressor, a relief device for said passage, means responsive to variations of pressure in said cylinder for operating said relief device, and a check valveinterposed between said relief device and said receiving means.

28. The combination with a compressor having a cylinder, of means controlled by variations in pressure within said cylinder for unloading said compressor, and `means operated by variations in pressure in said -cylinder and controlled by said unloading means for controlling communication between said cylinder and said unloading means.

29. The combination with a compressor having a cylinder, of means responsive to variations in pressure in said cylinder for unloading said compressor, and means for controlling communication between said cylinder and said unloading means, said conimunication controlling means being responsive to subnormal pressure in said cylinder' to open communication between said cylinder and unloading means, and being controlled by said unloading means to maintain said communication when said unloading means is in position to unload said compressor.

30. The combination with a compressor,

of a relief valve for venting said compressor to the atmosphere, means responsive to subnormal pressure within said compressor for operating said relief valve, and a check valve controlled by said operating means for controlling communication between said compressor and said operating means.

31. The eombinationwith a compressor, of a relief valve for venting said compressor to the atmosphere, a cylinder communicating. with the interior of said compressor, a piston in said cylinder for operating said relief valve, and a check valve for controlling communication between said compressor and cylinder, said check valve being held unseated by said piston when the latter is in position to open said relief valve.

32. The combination with a compressor cylinder, of a relief valve for vent-ing said compressor cylinder to the atmosphere, a cylinder communicable with the interior of the compressor cylinder,=a one-way check valve opening towards the compressor cylinder controlling the communication between the latter and the second mentioned` cylinder,y and a piston in said second mentioned cylinder for opening said relief valve and also operative in a given position thereof to hold said check valve open.

33. The combination of an air compressor cylinder having a. piston movable therein, inlet and discharge valves and a main unloader valve for said cylinder. an auxiliary unloader valve arranged beyond said discharge valves, and means responsive to a rvacuum condition in said cylinder proper for opening said auxiliary unloader valve to relieve the work on said piston.

34. The combination of an Vair compressor cylinder having a piston movable therein, inlet and discharge valves and a main unlca der valve for said cylinder, an auxiliary unloader valve beyond said discharge valves,

and means controlled by a vacuum condition in said cylinder proper cooperating with saidcauxiliary unloader valve to move the latter to relievev the work on said piston. 35. A compressor controlling mechanism ccmprisinga valve common to both ends of a compressor cylinder for controlling the load thereon, and means for controlling said common valve adapted to have direct communication with each end of the compressor cylinder, said latter means being actuated by pressure fluctuations in said ends.

36. A compressor unloading mechanism comprising a valve common to both ends of la compressor cylinder for controlling the load thereon. said valve controlling an atmospheric vent, and means for controlling actuation of'sald valve, havmg direct communication with each end of the compressor y cylinder, and means whereby said latter means is actuated by pressure iuctuations in said ends. f

37. A compressor controlling `mechanism comprising a valve common to both ends of a compressor cylinder for controlling the.

load thereon, and means for controlling said common valve adapted to have communication alternately with the cylinder ends.

38. The combination with a double acting compressor, of a common passage through which the fluid discharged from `said compressor passes to the receiver, valve means controlling said passage whereby to control the load on said compressor, and means for controlling said valve means adapted to have direct communication with each end of the compressor cylinder.

In testimony whereof I aiiix my signature.

HJALMAR T. BLOM.

Certificate of Correction.

Granted October 4, 1927, to HJALMAR T. BLOM.

It is hereby certied that error appears in the printed specification ot the abovenuinbered patent requiring correction as follows: Page 3, line 112, claim 10, strike out the semicolon; and that the said Letters Patent Should be read Withthis correction there-in that the saine may conform to the record of the case in the Patent Oice.

Signed and sealed this 1st day of November, A. D. 1927.

[SEAL] Patent No. 1,644,007.

M. J. MOORE, Acting @ammissioner of Patents. 

